1. Field of the Invention
The present invention relates to an orbiting vane compressor, and, more particularly, to a capacity-changing unit of an orbiting vane compressor that is capable of performing normal operation and no-load operation in inner and outer compression chambers through simple manipulation of a rotary valve plate, thereby easily changing the capacity of the compressor according to operation modes.
2. Description of the Related Art
Generally, an orbiting vane compressor is constructed to compress refrigerant gas introduced into a cylinder through an orbiting movement of an orbiting vane in the cylinder having an inlet port. Various types of orbiting vane compressors, which are classified based on their shapes, have been proposed.
FIG. 1 is a longitudinal sectional view illustrating the overall structure of a conventional rotary-type orbiting vane compressor. As shown in FIG. 1, a drive unit D and a compression unit P, which is disposed below the drive unit D, are mounted in a shell 1 while the drive unit D and the compression unit P are hermetically sealed. The drive unit D and the compression unit P are connected to each other via a vertical crankshaft 6, which has an eccentric part 6a. 
The drive unit D comprises: a stator 2 fixedly disposed in the shell 1; and a rotor 3 disposed in the stator 2 for rotating the crankshaft 6, which vertically extends through the rotor 3, when electric current is supplied to the rotor 3.
The compression unit P comprises an orbiting vane 4 for performing an orbiting movement in a cylinder 5 by the eccentric part 6a of the crankshaft 6. As the orbiting vane 4 performs the orbiting movement in the cylinder 5, refrigerant gas introduced into the cylinder 5 through an inlet port 51 is compressed. The cylinder 5 has an inner ring 52. Between the inner ring 52 and the inner wall of the cylinder 5 is defined an annular operation space 53. A wrap 40 of the orbiting vane 4 performs an orbiting movement in the operation space 53. As a result, compression chambers are formed at the inside and the outside of the wrap 40, respectively.
At the upper and lower parts of the compression unit P are disposed a main frame 7 and a subsidiary frame 7a, which support opposite ends of the crankshaft 6. The subsidiary frame 7a has a discharge chamber 8a, which is formed by a muffler 8. The discharge chamber 8a is connected to a pipe-shaped discharge channel 9, which extends vertically through the compression unit P and the main frame 7, such that the compressed refrigerant gas is discharged into the shell 1 through the discharge channel 9.
Unexplained reference numeral 11 indicates an inlet tube, 12 an outlet tube, and 10a an Oldham's ring for preventing rotation of the wrap 40 of the orbiting vane 4.
When electric current is supplied to the drive unit D, the rotor 3 of the drive unit D is rotated, and therefore, the crankshaft 6, which vertically extends through the rotor 3, is also rotated. As the crankshaft 6 is rotated, the orbiting vane 4 attached to the eccentric part 6a of the crankshaft 6 performs an orbiting movement.
As a result, the wrap 40 of the orbiting vane 4 performs an orbiting movement in the operation space 53 of the cylinder 5 to compress refrigerant gas introduced into the cylinder 5 through the inlet port 51 in the compression chambers formed at the inside and the outside of the wrap 40, respectively. The compressed refrigerant gas is discharged into the discharge chamber 8a through inner and outer outlet ports (not shown) formed at the cylinder 5 and the subsidiary frame 7a. The discharged high-pressure refrigerant gas is guided into the shell 1 through the discharge channel 9. Finally, the compressed refrigerant gas is discharged out of the shell 1 through the outlet tube 12.
FIG. 2 is a plan view, in section, illustrating the compressing operation of the conventional orbiting vane compressor shown in FIG. 1.
As shown in FIG. 2, the wrap 40 of the orbiting vane 4 of the compression unit P performs an orbiting movement in the operation space 53 of the cylinder 5, as indicated by arrows, to compress refrigerant gas introduced into the operation space 53 through the inlet port 51. The orbiting movement of the wrap 40 of the orbiting vane 4 will be described hereinafter in more detail.
At the initial orbiting position of the wrap 40 of the orbiting vane 4 of the compression unit P (i.e., the 0-degree orbiting position), refrigerant gas is introduced into an inner suction chamber A1, which is disposed at the inside of the wrap 40, through the inlet port 51, and compression is performed in an outer compression chamber B2, which is disposed at the outside of the wrap 40, while the outer compression chamber B2 does not communicate with the inlet port 51 and an outer outlet port 53b. Refrigerant gas is compressed in an inner compression chamber A2, and at the same time, the compressed refrigerant gas is discharged out of the inner compression chamber A2.
At the 90-degree orbiting position of the wrap 40 of the orbiting vane 4 of the compression unit P, the compression is still performed in the outer compression chamber B2, and almost all the compressed refrigerant gas is discharged out of the inner compression chamber A2 through an inner outlet port 53a. At this stage, an outer suction chamber B1 appears so that refrigerant gas is introduced into the outer suction chamber B1 through the inlet port 51.
At the 180-degree orbiting position of the wrap 40 of the orbiting vane 4 of the compression unit P, the inner suction chamber A1 disappears. Specifically, the inner suction chamber A1 is changed into the inner compression chamber A2, and therefore, compression is performed in the inner compression chamber A2. At this stage, the outer compression chamber B2 communicates with the outer outlet port 53b. Consequently, the compressed refrigerant gas is discharged out of the outer compression chamber B2 through the outer outlet port 53b. 
At the 270-degree orbiting position of the wrap 40 of the orbiting vane 4 of the compression unit P, almost all the compressed refrigerant gas is discharged out of the outer compression chamber B2 through the outer outlet port 53b, and the compression is still performed in the inner compression chamber A2. Also, compression is newly performed in the outer suction chamber B1. When the orbiting vane 4 of the compression unit P further performs the orbiting movement by 90 degrees, the outer suction chamber B1 disappears. Specifically, the outer suction chamber B1 is changed into the outer compression chamber B2, and therefore, the compression is continuously performed in the outer compression chamber B2. As a result, the wrap 40 of the orbiting vane 4 of the compression unit P is returned to the position where the orbiting movement of the orbiting vane 4 is initiated. In this way, a 360-degree-per-cycle orbiting movement of the wrap 40 of the orbiting vane 4 of the compression unit P is accomplished. The orbiting movement of the wrap 40 of the orbiting vane 4 of the compression unit P is performed in a continuous fashion.
Unexplained reference numeral 55 indicates a slider for maintaining the seal between the high-pressure and low-pressure parts.
FIG. 3 is a plan view, in section, illustrating another example of the compression unit of the conventional orbiting vane compressor shown in FIG. 1.
As shown in FIG. 3, an annular operation space 53 is formed in the cylinder 5. The annular operation space 53 has opposite ends separated from each other by a closing part 58. At one end of the operation space 53 is formed a side inlet port 51. At the other end of the operation space 53 are formed inner and outer outlet parts 53a and 53b. 
The wrap 40 is configured such that the length of the wrap 40 is less than that of the operation space 53. The wrap 40 is disposed in the operation space 53 such that a suction channel is formed between the end of the wrap 40 at the inlet port side and the operation space 53. Sealing is maintained between the inner and outer compression chambers by the slider 55 at the end of the wrap 40 at the outlet port side.
The outlet port side operation space 53 has a linear part 59 although the other part of the operation space 53 is approximately formed in the shape of a ring. Consequently, the slider 55 is disposed in the linear part 59 of the operation space 53 such that the slide 55 can be linearly reciprocated. The slider 55 is brought into tight contact with the outlet port side end of the wrap 40 by the discharge pressure of the compressed refrigerant gas, which is discharged through a gas discharge hole 57 of the operation space 53, whereby sealing is maintained between the high-pressure and the low-pressure parts.
Meanwhile, an energy-saving operation of a refrigerating apparatus or an air conditioning apparatus, such as a refrigerator or an air conditioner, is generally performed as follows. When the temperature in the refrigerator or the temperature in a room where the air conditioner is installed reaches a predetermined temperature, the operation of the compressor of the refrigerator or the air conditioner is stopped. When the temperature in the refrigerator or the temperature in the room exceeds the predetermined temperature, on the other hand, the operation of the compressor of the refrigerator or the air conditioner is initiated. In this way, the operation of the compressor is repetitively turned on and off. Generally, power consumption when the operation of the compressor is initiated is greater than power consumption when the compressor is normally operated. Furthermore, interference between the compressed gas in the compressor and the parts of the compressor is caused due to abrupt interruption of the compressor and initiation of the compressor, and therefore, the parts of the compressor are prematurely worn, which reduces the service life of the compressor.
For this reason, it is required to change the capacity of the compressor without the repetitive on/off operation of the compressor as described above. An inverter system may be used to change the capacity of the compressor. In the inverter system, the number of rotations of the motor is controlled to change the capacity of the compressor. However, the inverter system has problems in that expensive electric circuit control devices and relevant parts are needed. Consequently, the manufacturing costs of the compressor are increased, and therefore, the competitiveness of the product is decreased.